#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	double d = 0;
		int c = 1;
	for (int a = 1; a<= 100; a++)
	{
		d+= 1.0*c / a;
		c = -c;
	}
	printf("%lf", d);
	return 0;
}